lockscreen battery status: add off option (2/2)

Change-Id: Ie10015865f161e783dc394d467e456d51dc9fbbc

Conflicts:
	core/java/android/provider/Settings.java
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardMessageArea.java
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardUpdateMonitor.java